1. Field of the Invention
The present invention relates to an electronic component having an electronic component element which is mounted on a case substrate with a space therebetween and a manufacturing method for such an electronic component. More specifically, the present invention relates to an electronic component in which a bonding configuration of a substrate electrode on the case substrate and the electronic component element is improved and also relates to a method for manufacturing such an electronic component.
2. Description of the Related Art
Various electronic components, in which an electronic component element is mounted on a case substrate, have been proposed. For example, Japanese Unexamined Patent Application Publication No. 11-26628 discloses a package configuration for an electronic component shown in FIG. 7.
As seen in FIG. 7, in the electronic component 101, an energy-trap-type piezoelectric resonator 103 is mounted on a case substrate 102. Also, a cap 104 is fixed to the case substrate 102 so as to cover the energy-trap-type piezoelectric resonator 103.
The center portion in the longitudinal direction of the piezoelectric resonator 103 functions as a resonant portion, and resonance energy is confined in the resonant portion. The piezoelectric resonator 103 is fixed to the case substrate 102 with a space A therebetween so that the vibration in the resonant portion is not disturbed. In order to provide the space A, via-hole electrodes 105 and 106 are provided in the case substrate 102 such that they protrude upward beyond the upper surface 102a of the case substrate 102. The piezoelectric resonator 103 is bonded to the upper ends of the via-hole electrodes 105 and 106 by a conductive adhesive 108a and 108b. 
In the piezoelectric resonator disclosed in Japanese Unexamined Patent Application Publication No. 11-26628, vibration energy is almost entirely confined to the resonant portion. However, the vibration energy is not completely confined and leaked vibration travels to both ends in the longitudinal direction of the piezoelectric resonator 103. Accordingly, when the piezoelectric resonator 103 is bonded to and supported by the via-hole electrodes 105 and 106, the resonance characteristic may be degraded by the supporting configuration.
In particular, as the piezoelectric resonator 103 is miniaturized, the distance between the resonant portion and the end in the longitudinal direction of the piezoelectric resonator 103, that is, the length of a vibration dumping portion is decreased. Thus, degradation in the resonance characteristic due to the above-described supporting configuration becomes a big problem in miniaturization of the piezoelectric resonator.
Also, in the electronic component 101, the cap 104 must be provided in a precise position so that the cap 104 does not come into contact with the piezoelectric resonator 103. If the cap 104 is deviates from the precise proper position, the cap 104 may contact the piezoelectric resonator 103. Also, when the electronic component 101 is conveyed by sucking the upper surface of the cap 104 using a vacuum chuck, the electronic component 101 may not be held by the vacuum chuck if the cap 104 is positioned with only a slight deviation.
Incidentally, the diameter of the top of the above-described via-hole electrodes 105 and 106 is relatively small, and thus, adverse effects of the supporting configuration of the piezoelectric resonator 103 given to the resonance characteristic can be reduced, compared to the case where the piezoelectric resonator 103 is bonded to planar substrate electrodes. However, since the diameter of the via-hole electrodes 105 and 106 is small, positioning of the piezoelectric resonator 103 and the via-hole electrodes 105 and 106 must be performed with high accuracy.
That is, when the piezoelectric resonator 103 is mounted on the case substrate 102, positioning of the piezoelectric resonator 103 must be performed with high accuracy. Accordingly, the manufacturing process is complicated and an expensive positioning mechanism is needed.
The foregoing are also substantial problems in general electronic components, such as heater elements, which are required to be fixed to a case substrate with a predetermined space therebetween, as well as the energy-trap-type piezoelectric resonator.
In order to overcome the problems described above, preferred embodiments of the present invention provide an electronic component in which an electronic component element is mounted on a case substrate with a space therebetween, and degradation in the resonance characteristic due to the bonding configuration between a case substrate and an electronic component element is minimized, and in which the electronic component element is easily positioned and fixed to the case substrate, and a method for manufacturing the same.
In addition, preferred embodiments of the present invention provide an electronic component in which a cap can be easily positioned to a case substrate and mounted thereon and a method for manufacturing the same, in the above-described electronic component and the method for manufacturing the same.
An electronic component according to a preferred embodiment of the present invention includes a case substrate having first and second principal surfaces facing each other, a plurality of substrate electrodes disposed on at least the first principal surface, each substrate electrode having a substantially spherical outer surface, an electronic component element, which is mounted on the first principal surface with a space therebetween and which is supported by the plurality of substrate electrodes in a point-contact manner, and a conductive bonding material for bonding the electronic component element to the plurality of substrate electrodes.
Preferably, the electronic component element includes a substantially rectangular plate and is supported at both ends thereof in the longitudinal direction by the plurality of substrate electrodes in a point-contact manner, and the following formula is satisfied:
Lkxe2x88x922We less than Lp less than Lkxe2x88x92We 
where Lp is the length of the electronic component element in the longitudinal direction of the electronic component element, Lk is the length of the case substrate in the longitudinal direction of the electronic component element, and We is the length of the substrate electrode in the longitudinal direction of the electronic component element.
The electronic component may further comprise a cap having an opening in a lower portion, an opening edge thereof being fixed to the case substrate so as to cover the electronic component element.
Preferably, the cap has an insulative surface, the opening edge of the cap is in contact with the outer surfaces of the plurality of substrate electrodes, and the following formula is satisfied:
Lkxe2x88x92We less than Lc 
where Lc is the length of the cap in the longitudinal direction of the electronic component element.
In the electronic component according to preferred embodiments of the present invention, each of the substrate electrodes preferably includes an electrode layer formed by applying and baking a conductive paste, so that the outer surface of each substrate electrode is reliably substantially spherical shaped.
Preferably, the conductive bonding material is a flexible conductive adhesive, and thus degradation in the characteristic of the electronic component element due to the supporting configuration of the electronic component by the case substrate does not occur.
In the electronic component according to preferred embodiments of the present invention, although the electronic component element is not limited, an energy-trap-type piezoelectric resonator may be used.
A method for manufacturing an electronic component according to another preferred embodiment of the present invention includes steps of preparing a case substrate having first and second principal surfaces facing each other and a transfer plate made of a flexible material and having a plurality of grooves which extend in one direction and which are filled with a conductive paste, applying the conductive paste to at least the first principal surface by pressing the first principal surface into contact with one surface of the transfer plate and then removing the transfer plate, forming a plurality of substrate electrodes, each having a substantially spherical outer surface, on the first principal surface of the case substrate by baking the conductive paste, mounting an electronic component element on the case substrate provided with the substrate electrodes such that the electronic component element is spaced from the first principal surface and is supported by the plurality of substrate electrodes in a point-contact manner, and bonding the substrate electrodes of the case substrate to the electronic component element using a conductive bonding material.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.